Crank shaft



Nov. 11 A924 A. HIRTH CRANK SHAFT Filed DEG. 22. 1920 Y Y' n n 'u INVENTOR. f//fwf XM BY M.

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-Patented Nov. 11,1924. l

A \Nlr/ED s'rATEs ,14,768 PATET orion.

ALBERT HITH, OF GANNSTATT-STUTTGART, GERMANY, ASSIGNOR T AKTIEBOLAGET SVENSKA K'ULLAGERFABRIKEN, 0F GOTTENBORG, SWEDEN, A GORPOATION OF THE KINGDOM 0F SWEDEN. v

CRANK SHAFT.

Application led December 22, 1920. Serial No. 432,445.

To all whom t may concem:

Be it known that I, ALBERT HIRTH, a citizen of Germany, residing at Camistatt- Stuttgart, Germany, have invented certain 'new and useful Improvements in Crank Shafts, of which the following is a speciflcation, reference being had therein the accompanying drawing.l

My invention refers to vcrank shafts, and

lo more especially to crank shafts composed of a plurality of parts.

In high speed internal combustion engines for flying-machines, motor cars, launches,

and the like, it is the aim to achieve in- 15 creased reliability in working together with reduced resistances due to friction, and

economy of fuel as well as of lubricating oil.

In consideration of these points it appears desirable to employ ball bearings or 2o roller bearings for the main bearings of the motor.`

It is, however, very diicult to use such bearings with the customary multi-crank shafts. Either the bushes must be divided, i

of they must be made disproportionately lar e so as to allow of bringing them into position between the crank webs. Both v methods are known to present considerable disadvantages.

` Another possibility would consist in building up the crank itself from a number of separate component parts which would not be assembled until after the ball races had been slipped onto the parts of the shaft running in the bearing.

Experiments to this effect have already ,been made, but such built up shafts have not proved satisfactory owing to their giving rise to considerable trouble at the points of connection between the various parts. The connections either began to slacken during the Vworking of the engine and required constant supervision and rep-airing or, on lthebther hand, were-too hard toundo, if such a necessity arose, or too liable to damage when being taken to pieces, so that it became impossible to iit them together again accurately afterwards.

My invention now presents a new method of building up multi-crank shafts from indivi dual component parts which possesses the advantages offered by the built-up shaft, without having the disadvantages mentioned above. My invention substantially consiste sleeve.

in employing joints shapedl in a particular manner for connecting the crank pins and the journals with the crank web, the joints being constituted by teeth on the ends of the crank pin engaging and interlocking with corresponding teeth on the inner faces of the crank webs, with' the sides of the individual teeth sloping outwardly to their base, and the parts being suitably connected in fixed relations, as for instance by means of a bolt extending through the crank pin and engaged with the crank webs.

In the accompanying drawings:

Fig. 1 is a sectional elevation of a crank shaft constructed in accordance with my invention.

Fig. 2 is a transverse section of the saine on the line A-B as viewed in the direction of the arrows. l

Referring tothe drawings:

. The circular journal or crank pin 2 is connected with the iat crank webs 4 and 4 by means o-f teeth 2a on the opposite ends of the crank pin, which teeth engage and interlock with two circular series of teeth G projecting linwardly from the inner faces of the crank webs. The crank pin 2 is hollow, and through it and two aligned openings in the two crank webs, extends a locking bolt in the form of a hollow sleeve 7 and a head 8 screwed into the end of the At its end the sleeve 7 is provided with an annular head l0 which `is countersunk in the outer side of web 4;, and the head 8 is likewise countersunk in the outeti` side of web 4a, so that when the head is screwed into the. sleeve', the through bolt will be caused to engage the two webs and will draw them inwardly and force their teeth into interlocking engagement with the teeth on `the ends of the crank pin and there/by will hold the parts iXedly and rigidly in position. Inward of the crank pin 2 the Webs 'have connected with them in a manner similar to the connection of the crank pin 2, v

from the crank web a, these parts being con-'V nected together by a through bolt 1l similar in form and construction te ma rst described. The crank pin 1a at the right is similarly formed and similarly connected between the other web '-13 and the third web 4b by means of a through bolt 12 similar to the other through bolts. This latter web 4h has a crank pin 2a connected with its outer side, the said crank pin being provided, similar to the other crank pins, with end teeth which engage and interlock with similar end teeth 6c projecting outwardly from the face of the web 4b, the parts being connected together by a through bolt 13.

The crank pins 1, la and 2 are adapted to serve as the inner races of roller or ball bearings and they serve as well as the bearings of the crank shaft itself.

In the construction shown, the crank pins constituting the inner races for the roller or ball bearings are very short, and a corresponding saving in highgrade steel is thus effected. The width of the crank webs also is very` small. Moreover the whole construction is pleasing to the eye in consequence of the countersinking of the heads 8 and 10 of the through bolts. The comparatively large outer diameter of the toothed portions of the crank pins and webs, has the advantage of making the length of the crank web between the toothed portions very short. Since it is this part of thecrank web which is exposed to the greatest elastic deformation, owing to the effect of the forces acting upon it, the amount of these deformations is reduced to a minimum owing to the supporting action of the two surfaces, thus materially increasing the life of a shaft built up in this manner. The shape and circular pitch of the teeth iS chosen to suit the individual case. The circular pitch is in this case chosen with due regard to the fact that it should correspondl to thefangles at which the various cranks yof the crank shaft must 'be arranged in respect of one another. f

The whole design offers absolute accuracy as regards the necessity of all of the crank pinsdor journals being parallel, and all of the bearing journals being on one and the same axis, if the component parts are manufactured onspecial machines suited for the purpose. `This is an additional advantage in comparison withthe methods of manufacturing ymulti-crank shafts hitherto practised; it being customary to subject such multi-crank shafts to considerable finishing operations as it is not possible to manufacture them with accuracy in the rst instance.

It is to be noted that the teeth on the ends i of the crank pins and the teethon the faces of the webs which interlock therewith, have sharp edges and that the sides of the individual teeth slope outwardly from these edges to the base of the teeth as indicated on the crankpin 2a at the lower right-hand portion of Fig. 1. The interlocking teeth of this form 0n the webs and crank pins, brings about a very positive locking of the parts when the through bolts are drawn up, as the slopin surfaces of the teeth act with a wedge ing e ect on each other and insure an absolute /inal positioning of the parts without looseness or liability of displacement.

I claim: v

1. A built up crank shaft comprising in combination, ftwo crank webs and an intermediate crank pin, the inner faces of .said webs being provided with sharp edged teeth projecting inwardly therefrom, and the end faces of said pin being provided with similarly formed teeth engaging the teeth on the webs.

2. A built up crank shaft comprisingin combination, two crank webs and an intermediate crank pin, the end faces of said pin and the inner faces of said webs being provided with sharp edged teethin interlocking engagement with each other, and a through bolt extending into thesaid crank pin and engaging the webs to firmly hold said teeth y 1n permanent engagement substantially as set forth.

3. A built up crank shaft comprising in combination, two crank webs and an interf stantially as set forth.

4. A built up crank shaft comprising in combination, two crank webs and an inter- Imediate crank pin, the inner faces of said webs having sharp edged teeth extending inwardly therefrom with the sides of the individual teeth sloping outwardly to the base, and the end faces 'of said pm being provided with similarly formed teeth engaging the teeth on the webs, and a through boltY engaging the webs and acting to force the teeth into interlocking engagement with each other. y

In testimony whereof, I have affixed my signature hereto. e

ALBERT IHIRTH.

CERTIFICATE 0F CORRECTWN.

l Patent No. 1,514,768. Granted November 11, 1m, to'

' Acnnn'r Hmm.

It is herebyvcertified that the above numbered patent was erroneously issued to' "Aktiebolaget Svenska Kull'agerfnbriken, of Gottenborg, Sweden, n corporation oi the Kingdom of Sweden?, as assignee of the entire interest in said invention, whereas said patent should havebeen issued to the inventor said "Hirth and Aktiebolaget Svenska Knliageriabriken, of` Gottenhorg, Sweden n corporation of the Kingdom of Sweden", said corporation' being assignee of one-half interest only in said invention, as shown hy. the recordsof assignments in this office; and that the said Letters Patent shouid `be read with this correction therein that the same may conform to the record of the casein the Patent ffice.

' Si and sealed this lith day oi December, A. D. 1928.4

- M. J. Moore, (Sedi) Acting Commissioner oi Patents. 

